System and method for strengthening heavy metal, nitrogen and phosphorus combined pollution wastewater treatment

Abstract

The invention belongs to the technical field of water purification, and particularly relates to a system and a method for strengthening heavy metal, nitrogen and phosphorus combined pollution wastewater treatment. The system comprises a circulating type ecological ditch main body, an ecological planting unit and a magnetic field generating device, the circulating type ecological ditch main body comprises ditch side walls and a plurality of flow guide walls, water enters from one end, and water exits from the other end; the ecological planting unit comprises aquatic plants, microorganisms, a soil matrix and a filter material mixing layer; the magnetic field generating device comprises a plurality of permanent magnetic ferrite magnets. According to the invention, permanent magnets are embedded into a circulating ecological ditch to form a magnetic field-microorganism-aquatic plant-filter material matrix wastewater treatment system, so that some microorganisms can better adapt to a wastewater environment containing heavy metals, and pollutants such as heavy metals and nitrogen and phosphorus in wastewater are effectively degraded; the method has the advantages of low cost, no secondary pollution, high environmental adaptability and the like, and has popularization potential in the market.

Description

Technical Field

[0001] The invention belongs to the technical field of water purification, and specifically relates to a system and method for strengthening the treatment of wastewater contaminated by heavy metals, nitrogen and phosphorus. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Ecological ditches are a water treatment technology that simulates natural wetland ecosystems. By planting aquatic plants and introducing microorganisms in the ditches, physical, chemical and biological treatment methods are used to degrade pollutants such as carbon, nitrogen and phosphorus in wastewater. However, as heavy metal components are widely used in various products such as feed additives and cosmetics, the content of heavy metals in agricultural and domestic wastewater has gradually increased, which has affected the wastewater purification effect of traditional ecological ditches to a certain extent and caused damage to the ecological environment.

[0004] Nowadays, the research on ecological ditches is developing towards how to improve the efficiency of ecological purification. Circulating ecological ditches can make sewage have a longer hydraulic retention time, and have high purification efficiency for harmful substances such as nitrogen and phosphorus. They are often used as agricultural wastewater treatment devices, but they cannot effectively remove heavy metals, nitrogen and phosphorus in heavy metal-containing wastewater. Therefore, a system based on circulating ecological ditches with low cost, no secondary pollution, and strong environmental adaptability for strengthening the treatment of heavy metal and nitrogen and phosphorus composite pollution wastewater is proposed, which is the key to the effective purification of pollutants, in order to reduce the impact of heavy metal pollutants on the ecological environment. Summary of the invention

[0005] In order to solve the problems existing in the above-mentioned background technology, the present invention provides a system and method for strengthening the treatment of wastewater polluted by heavy metals, nitrogen and phosphorus. The magnetic effect generated by the introduction of a magnetic field generating device can not only improve the activity and metabolic function of microorganisms in the circulating ecological ditch, so that certain microorganisms have a stronger treatment ability for heavy metal pollutants, but also enhance the enrichment capacity of the soil matrix and filter material mixed layer, increase the biomass of aquatic plants, etc. Through the joint action of multiple factors, the removal effect of pollutants such as carbon, nitrogen, phosphorus and heavy metals can be enhanced, and the pollution level in the environment can be greatly reduced.

[0006] This system is an effective solution that can enhance the decontamination effect in response to the situation where wastewater containing heavy metals affects the activity of microorganisms, biomass of aquatic plants, metabolic functions, etc., resulting in a decrease in the removal effect of pollutants. The system is suitable for treating complex polluted wastewater including but not limited to heavy metals such as iron ions, manganese ions, copper ions, and zinc ions.

[0007] In order to achieve the above-mentioned object, the first aspect of the present invention provides a system for strengthening the treatment of wastewater contaminated by heavy metals, nitrogen and phosphorus, which specifically includes: a circulating ecological ditch body, an ecological planting unit and a magnetic field generating device;

[0008] The main body of the circulating ecological ditch includes a ditch side wall and a plurality of diversion walls, which are staggered on the left and right sides and spaced apart inside the ditch side wall, with water entering at one end and discharging at the other end, so that the wastewater forms a "Z"-shaped water flow channel in the main body of the circulating ecological ditch;

[0009] The ecological planting unit is composed of aquatic plants, soil matrix and filter material mixed layer from top to bottom, the roots of aquatic plants are fixed in the soil matrix and filter material mixed layer, and microorganisms are enriched in the soil matrix and filter material surface;

[0010] The magnetic field generating device comprises a plurality of permanent ferrite magnets, which are fixed on the guide wall of the circulation ditch body in a vertical manner with opposite magnetic poles.

[0011] The second aspect of the present invention provides a method for treating heavy metal, nitrogen and phosphorus composite polluted wastewater using the above-mentioned system, specifically comprising: the composite polluted wastewater to be treated continuously takes in water from one end of a circulating ecological ditch, the wastewater interacts with the ecological planting unit and the magnetic field generating device in a "Z"-shaped water flow, so as to achieve ecological interception and efficient degradation of heavy metals and nitrogen, phosphorus and other pollutants, and the composite polluted wastewater is purified and continuously discharged from the other end of the circulating ecological ditch.

[0012] One or more embodiments of the present invention have at least the following beneficial effects:

[0013] First, this application constructs a magnetic field-embedded system for enhanced treatment of heavy metal, nitrogen and phosphorus complex-polluted wastewater based on a circulating ecological ditch. Through the action of a magnetic field of appropriate intensity, it can promote the activity of microorganisms in the circulating ecological ditch, enhance the enrichment capacity of the soil matrix and filter material mixed layer, increase the biomass of aquatic plants, etc., thereby improving the purification efficiency of heavy metal pollutants in the circulating ecological ditch. It has the advantages of low cost, no secondary pollution, and strong environmental adaptability, and has the potential for promotion in the market.

[0014] Secondly, the magnetic effect produced by the magnetic field generator can promote the dissolution of oxygen in water, enhance the atmospheric reoxygenation capacity and the oxygen secretion capacity of aquatic plant roots, increase the active oxygen content in water, build an aerobic-anaerobic-anoxic environment in the system, and improve the purification efficiency of carbon, nitrogen, phosphorus and other pollutants in the main body of the circulating ecological ditch. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0016] Figure 1 A top view of the structure of one embodiment of the system of the present invention;

[0017] Figure 2 A structural cross-sectional view of one embodiment of the system of the present invention;

[0018] Figure 3 A schematic diagram of the installation position of a permanent ferrite magnet in one embodiment of the system of the present invention;

[0019] Figure 4 A schematic diagram of the magnetic field intensity distribution of one of the baffle sections of the system of the present invention;

[0020] Figure 5 A bar graph showing the pollutant removal effect of Example 1;

[0021] Figure 6 A bar graph showing the pollutant removal effect of Example 2.

[0022] Among them: 10. Circulating ecological ditch main body; 11. Side wall; 12. Diversion wall; 20. Ecological planting unit; 21. Aquatic plants; 22. Soil matrix and filter material mixed layer; 23. Microorganisms; 30. Magnetic field generating device; 31. Permanent ferrite magnet. DETAILED DESCRIPTION

[0023] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0024] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0025] As introduced in the background technology, the existing ecological ditch cannot effectively treat the wastewater containing heavy metals, nitrogen and phosphorus compound pollution. In order to solve the above technical problems, the first aspect of the present invention proposes a system for strengthening the treatment of wastewater containing heavy metals, nitrogen and phosphorus compound pollution, which specifically includes: a circulating ecological ditch body, an ecological planting unit and a magnetic field generating device;

[0026] The main body of the circulating ecological ditch includes ditch side walls and several diversion walls. The diversion walls are staggered on the inside of the ditch side walls and are spaced apart. Water enters at one end and flows out at the other end, so that the wastewater forms a "Z"-shaped water flow channel in the main body of the circulating ecological ditch.

[0027] Furthermore, the main side walls and diversion walls of the circulating ecological ditch are composed of ecological porous bricks;

[0028] Furthermore, the main body of the circulating ecological ditch is 100 cm wide, 100 cm high, and less than 200 m long. The thickness of the diversion wall is 50 cm, the interval between every two diversion walls is 50 cm, the first diversion wall is greater than 50 cm from the water inlet, and the last diversion wall is greater than 50 cm from the water outlet;

[0029] Furthermore, the thickness of the soil matrix and filter material mixed layer should be greater than 20 cm so that the roots of aquatic plants can be firmly fixed in the soil matrix and filter material mixed layer.

[0030] The ecological planting unit consists of aquatic plants, soil matrix and filter material mixed layer from top to bottom. The roots of aquatic plants are fixed in the soil matrix and filter material mixed layer, and microorganisms are enriched in the soil matrix and filter material surface.

[0031] Furthermore, the aquatic plants are mainly submerged, emergent and slope protection plants, including but not limited to purple iris, yellow iris, iris, sedge, reed and canna, with a planting density of 80 to 100 plants / m2;

[0032] Furthermore, the filter material is composed of crushed stone with a particle size of 1 to 5 cm, including but not limited to one or more of abandoned magnetite, limestone, zeolite, shale, slag, and gravel materials, and the soil matrix and the filter material are uniformly mixed in a ratio of 1:1 to 1:5 to form a soil matrix and filter material mixed layer;

[0033] Preferably, the waste magnetite is uniformly mixed with other filter materials in a ratio of 1:3 to 1:10, which can not only realize the recycling of waste, but also further expand the magnetization area to enhance the magnetization effect inside the system;

[0034] The magnetic field generating device comprises a plurality of permanent ferrite magnets, which are fixed on the guide wall of the circulation ditch body in a vertical manner with opposite magnetic poles;

[0035] Furthermore, to ensure that there is a suitable magnetic field strength in the system, each guide wall has a total of 8 permanent ferrite magnets, which are fixed on the guide wall in the form of 4 rows and 2 columns, and each set of magnetic field generating devices has a total of 16 permanent ferrite magnets;

[0036] Furthermore, the permanent ferrite magnet is fixed to the diversion wall of the main body of the circulating ecological ditch in the form of mechanical installation, and the permanent magnet is firmly fixed to the diversion wall by mechanical parts such as bolts and screws, so that the permanent magnet can be fixed in the composite pollution wastewater treatment system for a long time;

[0037] Preferably, the performance model of the permanent ferrite magnet is Y25, and the length, width and height are 150mm×100mm×20mm respectively, so that the magnetic field strength inside the circulating ecological ditch is 5-20mT. Figure 4 Schematic diagram of magnetic field intensity distribution of one of the baffle sections of the system described in the present invention.

[0038] The present invention fixes the permanent ferrite magnet on the diversion wall of the main body of the circulating ecological ditch, and the main purposes are three aspects:

[0039] (1) The diversion wall can form a "Z"-shaped water flow channel for complex polluted wastewater in the circulating ecological ditch, so that the wastewater can fully contact with the aquatic plants, soil matrix and filter material mixed layer, and microorganisms in the system, thereby promoting the removal of pollutants such as phosphorus and heavy metals.

[0040] (2) The introduction of a magnetic field generator can not only improve the activity and metabolic function of microorganisms in the circulating ecological ditch, making some microorganisms more capable of treating heavy metal pollutants, but also enhance the enrichment capacity of the soil matrix and filter material mixed layer, increase the biomass of aquatic plants, etc. Through the combined effect of multiple factors, it can enhance the removal effect of pollutants such as carbon, nitrogen, phosphorus and heavy metals, and greatly reduce the pollution level in the environment.

[0041] (3) The introduction of a magnetic field generator can promote the dissolution of oxygen in water, enhance the atmospheric reoxygenation capacity and the oxygen secretion capacity of aquatic plant roots, increase the active oxygen content in water, construct an aerobic-anaerobic-anoxic environment in the system, and improve the purification efficiency of circulating ecological ditches for pollutants such as carbon, nitrogen, and phosphorus.

[0042] Based on the above effects, the present invention solves the problem of decreased microbial activity and aquatic plant biomass under the influence of heavy metals and poor pollutant removal effect by constructing a system for enhanced treatment of heavy metal, nitrogen and phosphorus complex polluted wastewater by organically combining "magnetic field-microorganism-aquatic plant-filter material matrix". The system is suitable for treating complex polluted wastewater including but not limited to heavy metals such as iron ions, manganese ions, copper ions, zinc ions, etc.

[0043] In one or more embodiments of the present invention, the effective water depth of the heavy metal and nitrogen-phosphorus composite polluted wastewater in the circulating ecological ditch is at least 0.5m and at most 1.0m. If the effective water depth is too low, it will affect the dissolved oxygen concentration of the wastewater and make it impossible for microorganisms to effectively carry out denitrification. If the effective water depth is too high, it will overflow the channel and affect the decontamination effect.

[0044] The second aspect of the present invention provides a method for treating heavy metal, nitrogen and phosphorus composite polluted wastewater using the above-mentioned system, specifically comprising: the composite polluted wastewater to be treated continuously takes in water from one end of the circulating ecological ditch main body, the wastewater interacts with the ecological planting unit and the magnetic field generating device in a "Z"-shaped water flow, so as to achieve ecological interception and efficient degradation of heavy metals and nitrogen, phosphorus and other pollutants, and the composite polluted wastewater is purified and continuously discharged from the other end of the circulating ecological ditch.

[0045] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0046] Example 1

[0047] According to the system described in the present invention, a system for enhanced treatment of wastewater polluted by heavy metals, nitrogen and phosphorus is constructed in the laboratory. The main body of the circulating ecological ditch is a rectangular parallelepiped with a length, width and height of 250cm×140cm×120cm, an effective length, an effective width and an effective height of 250cm×100cm×100cm, and a thickness of the mixed layer of soil matrix and filter material of 20cm.

[0048] The main body of the circulating ecological ditch is provided with a ditch side wall and two diversion walls, the ditch side wall and the diversion wall are made of ecological porous bricks, the diversion walls are staggered on the left and right sides of the inner side of the ditch side wall and are distributed at intervals of 50 cm, the first diversion wall is 50 cm away from the water inlet, and the second diversion wall is 50 cm away from the water outlet;

[0049] The system for strengthening the treatment of wastewater contaminated by heavy metals, nitrogen and phosphorus is composed of aquatic plants, soil matrix and filter material mixed layer from top to bottom, the roots of aquatic plants are fixed in the soil matrix and filter material mixed layer, and microorganisms are enriched in the soil matrix and filter material surface. Purple iris is planted on this system, and the microorganisms come from the activated sludge of the aerobic aeration tank of the sewage treatment plant.

[0050] The system for strengthening the treatment of wastewater contaminated by heavy metals, nitrogen and phosphorus uses a filter material with a particle size of 1 to 5 cm, which is obtained by uniformly mixing waste magnetite and gravel in a ratio of 1:5, and then uniformly mixing native soil and filter material in a ratio of 1:1 to obtain a soil matrix and filter material mixed layer.

[0051] The system for strengthening the treatment of heavy metal and nitrogen and phosphorus composite pollution wastewater includes a set of magnetic field generating devices, using a total of 16 permanent ferrite magnets, the performance strength of the permanent ferrite magnets is Y25, the length, width and height are 150mm×100mm×25mm respectively, and they are fixed on the diversion wall of the main body of the circulating ecological ditch in the form of 4 rows and 2 columns. The longitudinal distance between each two permanent magnets is 40mm and the horizontal distance is 150mm. 8 permanent ferrite magnets are installed on each diversion wall. The magnetic poles of the two corresponding magnets are opposite, so that the internal magnetic field strength of the system is 5-20mT. Figure 4 The diagram is a schematic diagram of the magnetic field intensity distribution of one of the baffle sections of the system of the present invention. The permanent ferrite magnet is fixed on the diversion wall of the main body of the circulating ecological ditch in the form of mechanical installation, and is firmly fixed on the diversion wall by mechanical parts such as bolts and screws, so that the permanent magnet can be fixed in the composite pollution wastewater treatment system for a long time.

[0052] This system for strengthening the treatment of wastewater contaminated by heavy metals, nitrogen and phosphorus was used to continuously add water containing heavy metals Fe 3+ , Mn 2+ , Cu 2+ 、Zn 2+ The combined polluted wastewater has an effective water depth of 0.8m and the effluent quality is monitored. Figure 5 Contains heavy metal Fe 3+ , Mn 2+ , Cu 2+ 、Zn 2+ The pollutant removal effect diagram of the control group and experimental group of the composite polluted wastewater shows that the pollutant removal effect when the magnetic field is applied is significantly better than that when no magnetic field is applied.

[0053] The chemical oxygen demand concentration of the composite polluted wastewater entering the system is controlled to be 120mg / L, the total nitrogen concentration is 40mg / L, the total phosphorus concentration is 5mg / L, and the heavy metal Fe 3+ The concentration is 2 mg / L. After the process described in this example, the chemical oxygen demand, total nitrogen, total phosphorus, heavy metal Fe 3+ The average effluent concentrations reached 19.32 mg / L, 9.25 mg / L, 1.26 mg / L and 0.24 mg / L respectively.

[0054] The chemical oxygen demand concentration of the composite polluted wastewater entering the system is controlled to be 120mg / L, the total nitrogen concentration is 40mg / L, the total phosphorus concentration is 5mg / L, and the heavy metal Mn 2+ The ion concentration is 2 mg / L. After the process described in this embodiment, the chemical oxygen demand, total nitrogen, total phosphorus, heavy metal Mn 2+The average effluent concentrations reached 16.13 mg / L, 7.9 mg / L, 1.38 mg / L and 0.93 mg / L respectively.

[0055] The chemical oxygen demand concentration of the composite polluted wastewater entering the system is controlled to be 120mg / L, the total nitrogen concentration is 40mg / L, the total phosphorus concentration is 5mg / L, and the heavy metal Cu 2+ The concentration is 0.5 mg / L. After the process described in this example, the chemical oxygen demand, total nitrogen, total phosphorus, heavy metal Cu 2+ The average effluent concentrations were 21.7 mg / L, 11.42 mg / L, 1.66 mg / L and 0.18 mg / L respectively.

[0056] The chemical oxygen demand concentration of the composite polluted wastewater entering the system is controlled to be 120mg / L, the total nitrogen concentration is 40mg / L, the total phosphorus concentration is 5mg / L, and the heavy metal Zn 2+ The concentration is 1 mg / L. After the process described in this example, the chemical oxygen demand, total nitrogen, total phosphorus, heavy metal Zn 2+ The average effluent concentrations reached 20.85 mg / L, 12.38 mg / L, 1.25 mg / L and 0.47 mg / L respectively.

[0057] Example 2

[0058] According to the system described in the present invention, a system for strengthening the treatment of wastewater polluted by heavy metals, nitrogen and phosphorus was constructed in a suburb of Taiyuan City, Shanxi Province. The main body of the circulating ecological ditch is a rectangular parallelepiped with a length, width and height of 650cm×140cm×120cm, respectively, an effective length, effective width and effective height of 650cm×100cm×100cm, respectively, and a thickness of the mixed layer of soil matrix and filter material of 20cm.

[0059] The main body of the circulating ecological ditch is provided with a ditch side wall and 5 diversion walls, which are made of ecological porous bricks. The diversion walls are staggered on the left and right sides of the inner side of the ditch side wall and are distributed at intervals of 50 cm. The first diversion wall is 100 cm away from the water inlet, and the fifth diversion wall is 100 cm away from the water outlet.

[0060] The system for strengthening the treatment of wastewater contaminated by heavy metals, nitrogen and phosphorus is composed of aquatic plants, soil matrix and filter material mixed layer from top to bottom, the roots of aquatic plants are fixed in the soil matrix and filter material mixed layer, and microorganisms are enriched in the soil matrix and filter material surface. Purple iris is planted on this system, and the microorganisms come from the activated sludge of the aerobic aeration tank of the sewage treatment plant.

[0061] The system for strengthening the treatment of wastewater contaminated by heavy metals, nitrogen and phosphorus uses a filter material with a particle size of 1 to 5 cm, which is obtained by uniformly mixing waste magnetite and gravel in a ratio of 1:5, and then uniformly mixing native soil and filter material in a ratio of 1:1 to obtain a soil matrix and filter material mixed layer.

[0062] The system for strengthening the treatment of heavy metal and nitrogen and phosphorus composite pollution wastewater includes 4 sets of magnetic field generating devices, using a total of 64 permanent ferrite magnets, the performance strength of the permanent ferrite magnets is Y25, the length, width and height are 150mm×100mm×25mm respectively, and they are fixed on the diversion wall of the main body of the circulating ecological ditch in the form of 4 rows and 2 columns. The longitudinal distance between each two permanent magnets is 40mm and the horizontal distance is 150mm. 8 permanent ferrite magnets are installed on each diversion wall. The magnetic poles of the two corresponding magnets are opposite, so that the internal magnetic field strength of the system is 5-20mT. Figure 4 The diagram is a schematic diagram of the magnetic field intensity distribution of one of the baffle sections of the system of the present invention. The permanent ferrite magnet is fixed on the diversion wall of the main body of the circulating ecological ditch in the form of mechanical installation, and is firmly fixed on the diversion wall by mechanical parts such as bolts and screws, so that the permanent magnet can be fixed in the composite pollution wastewater treatment system for a long time.

[0063] This system for strengthening the treatment of wastewater contaminated by heavy metals, nitrogen and phosphorus was used to continuously add water containing heavy metals Fe 3+ , Mn 2+ The combined polluted wastewater has an effective water depth of 0.5m and the effluent quality is monitored. Figure 6 Contains heavy metal Fe 3+ , Mn 2+ The pollutant removal effect diagram of the control group and experimental group of the composite polluted wastewater shows that the pollutant removal effect when the magnetic field is applied is significantly better than that when no magnetic field is applied.

[0064] The chemical oxygen demand concentration of the composite polluted wastewater entering the system is controlled to be 400mg / L, the total nitrogen concentration is 80mg / L, the total phosphorus concentration is 10mg / L, and the heavy metal Fe 3+ The concentration is 5 mg / L. After the process described in this example, the chemical oxygen demand, total nitrogen, total phosphorus, heavy metal Fe 3+ The average effluent concentrations were 67.18 mg / L, 24.46 mg / L, 2.32 mg / L and 1.53 mg / L respectively.

[0065] The chemical oxygen demand concentration of the composite polluted wastewater entering the system is controlled to be 400 mg / L, the total nitrogen concentration is 80 mg / L, the total phosphorus concentration is 10 mg / L, and the heavy metal Mn 2+The concentration is 5 mg / L. After the process described in this example, the chemical oxygen demand, total nitrogen, total phosphorus, heavy metal Mn 2+ The average effluent concentrations were 64.37 mg / L, 21.14 mg / L, 2.9 mg / L and 2.02 mg / L respectively.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A system for strengthening the treatment of wastewater contaminated by heavy metals, nitrogen and phosphorus, comprising a circulating ecological ditch body (10), an ecological planting unit (20) and a magnetic field generating device (30); characterized in that: The circulating ecological ditch body (10) comprises a ditch side wall (11) and a plurality of diversion walls (12), wherein the diversion walls (12) are staggered on the left and right sides and arranged at intervals inside the ditch side wall (11); The ecological planting unit (20) comprises, from top to bottom, aquatic plants (21), a soil matrix and a filter material mixed layer (23), wherein the roots of the aquatic plants are fixed in the soil matrix and the filter material mixed layer, and the microorganisms (22) are enriched in the soil matrix and the filter material surface; The magnetic field generating device (30) comprises a plurality of permanent ferrite magnets (31), and the permanent ferrite magnets (31) are fixed on the guide wall (12) of the main body of the circulating ecological ditch in a vertical manner with opposite magnetic poles.

2. The system for strengthening the treatment of wastewater contaminated by heavy metals, nitrogen and phosphorus as claimed in claim 1, characterized in that: The circulating ecological ditch body (10) has an effective width of 100 cm, an effective height of 100 cm, and a length of less than 200 m.

3. The system for strengthening the treatment of wastewater contaminated by heavy metals, nitrogen and phosphorus as claimed in claim 1, characterized in that: The thickness of the guide wall (12) is 50 cm, the interval between every two guide walls (12) is 50 cm, the first guide wall (12) is greater than 50 cm away from the water inlet, and the last guide wall (12) is greater than 50 cm away from the water outlet.

4. The system for strengthening the treatment of wastewater contaminated by heavy metals, nitrogen and phosphorus as claimed in claim 1, characterized in that: The side wall (11) and the guide wall (12) are made of ecological porous bricks.

5. The system for strengthening the treatment of wastewater contaminated by heavy metals, nitrogen and phosphorus as claimed in claim 1, characterized in that: The aquatic plants (21) in the ecological planting unit are submerged, emergent and slope protection plants, and the planting density is 80 to 100 plants / m 2 .

6. The system for strengthening the treatment of wastewater contaminated by heavy metals, nitrogen and phosphorus as claimed in claim 1, characterized in that: The filter material of the soil matrix and filter material mixed layer (23) is composed of crushed stones with a particle size of 1 to 5 cm.

7. The system for strengthening the treatment of wastewater contaminated by heavy metals, nitrogen and phosphorus as claimed in claim 7, characterized in that: The filter material is composed of one or more of waste magnetite, limestone, zeolite, shale, slag and gravel materials, and is evenly mixed with a soil matrix at a ratio of 1:1 to 5:1 to form a soil matrix and filter material mixed layer (23).

8. The system for strengthening the treatment of wastewater contaminated by heavy metals, nitrogen and phosphorus as claimed in claim 1, characterized in that: The permanent ferrite magnet (31) is fixed on the guide wall (12) of the circulating ecological ditch body (10) in a mechanically mounted manner.

9. The system for strengthening the treatment of wastewater contaminated by heavy metals, nitrogen and phosphorus as claimed in claim 9, characterized in that: The performance model of the permanent ferrite magnet (31) is Y25, and the length, width and height are 150mm×100mm×20mm respectively, so that the magnetic field strength inside the circulating ecological ditch is 5-20mT.

10. A method for strengthening the treatment of wastewater contaminated by heavy metals, nitrogen and phosphorus, which is implemented by using the system for strengthening the treatment of wastewater contaminated by heavy metals, nitrogen and phosphorus according to any one of claims 1 to 9, characterized in that: The composite polluted wastewater to be treated continuously enters from one end of the circulating ecological ditch main body (10), with an effective water depth of 0.5 to 1.0 m. The wastewater interacts with the ecological planting unit (20) and the magnetic field generating device (30) in a "Z"-shaped water flow, thereby achieving ecological interception and efficient degradation of pollutants such as heavy metals, nitrogen and phosphorus. After being purified, the composite polluted wastewater continuously flows out from the other end of the circulating ecological ditch main body (10).

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